The invention relates to gas turbine casings, and more particularly, but not exclusively, to gas turbine fan casings for aeroengines.
In a gas turbine aeroengine, the fan casing performs several functions. It defines the inlet passage for admitting air into the engine, and it supports an abradable material facing the tips of the fan blades, the abradable material generally itself being supported by a cellular structure.
Casing such as fan casings used to be made out of metal material, but they are now made out of composite material, i.e. from a fiber preform densified by an organic matrix, thus making it possible to make parts of overall weight that is less than that of the same parts when they are made out of metal, while still presenting mechanical strength that is at least equivalent if not stronger. Fabricating a fan casing out of organic matrix composite material is described in particular in Document EP 1 961 923.
A fan casing is one of the parts defining a “fire” zone in the meaning of aviation certification. In this context, it must be considered as being a fire wall between the nacelle compartment situated on the outside of the casing and the flow passage defined on the inside of the casing, and it must satisfy the associated regulatory requirements.
Nevertheless, during fire testing, it has been found that extinguishing flames present on the outside of the casing, i.e. in the nacelle compartment of the engine, can be difficult, even after switching off the burner.